Once local and irregular, time-keeping became universal and linear in 311 BCE

Paul J Kosmin in Aeon:

What year is it? It’s 2019, obviously. An easy question. Last year was 2018. Next year will be 2020. We are confident that a century ago it was 1919, and in 1,000 years it will be 3019, if there is anyone left to name it. All of us are fluent with these years; we, and most of the world, use them without thinking. They are ubiquitous. As a child I used to line up my pennies by year of minting, and now I carefully note dates of publication in my scholarly articles.

Now, imagine inhabiting a world without such a numbered timeline for ordering current events, memories and future hopes. For from earliest recorded history right up to the years after Alexander the Great’s conquests in the late 4th century BCE, historical time – the public and annual marking of the passage of years – could be measured only in three ways: by unique events, by annual offices, or by royal lifecycles.

In ancient Mesopotamia, years could be designated by an outstanding event of the preceding 12 months: something could be said to happen, for instance, in the year when king Naram-Sin reached the sources of the Tigris and Euphrates river, or when king Enlil-bani made for the god Ninurta three very large copper statues.

More here.